Electrical condenser



' F. w. DANE ELECTRICAL CONDENSER May 2? 1924;.

Filed April 5", 1920 We mof Massachusetts,

Patented it/lay 27, 1924. i

I teat-W. near sea area.

FRANCIS W. DANE, OF HAMILTON, MASSACHUSETTS, ASSIGNOR TO WIRELESS SPE-' CIALTY APPARATUS COMPANY, OF BOSTON, MASSACHUSETTS, A CORPORATION Oil NEW YORK.

Application filed April 3',

citizen of the United States, residin at Hamilton, in the county of LSSGX and btate have invented certain Improvements in Electrical Condensers, of which the following description, in connection with the accompanying drawings, is a specification, like reference characters on the drawings indicating like parts in the several figures.

The usual method practised commercially of making electrical condensers consists in assembling alternate sheets of conducting and dielectric materials, the materials used in the better class of condensers consisting of mica and metal foil. The sheets of mica and foil are secured together by a suitable insulating material such as paraffin, adhesive varnish, or the like. It has been determined that the maximum capacity is produced when the insulating material be-.

tween the foil and the mica is reduced to a minimum approaching the ideal case of moecular contact between the foil and the mica. It has likewise been determined that the condenser losses are less if the insulating filler between the foil and'the mica is reduced to a minimum, since the dielectric.

losses in mica are smaller than the dielectric losses in the insulating materials. It has also been determined that-the resistance of the condenser to breaking down either undertest or while in use depends on reducing, so far as possible, the presence of anything between the conducting elements except the mica. In other words, the presence of air spaces, voids, blisters, or even-of the insulating filler itself, is detrimental from an electrical standpoint. For instance,. the

resence of a void or bubble between a sheet of foil and the next adjacent sheet of mica is very liable to cause a brush discharge of ELECTRICAL oonnnnsnn,

1920. Senal Nb. 371,153.

I foil into intimate contact with each other and to heat the stack ,while still in the clamp, the purpose being to squeeze out from between the sheets any surplus insulating filler and also any air or gas that might be pocketed between said sheets. This expedient re-,

duces the liability of a break down due to the causes above mentioned. It does not,

however, entirely eliminate trouble from these causes and the present invention is directed to the improvement of the processes of marking condensers with the object ofie'ffecting a further reduction in the defects'of In other words, the inventhis character. tion aims to improve theprocess of manufacturing condensers with a view particularly to reducing to a minimum the presence of voids, bubbles, or adhesive material be-. tween the layers of conducting and dielec-v tric material that make up the condenser.

For the purpose of clearly disclosing the process of the present invention it will-be herein described 'in connection with a novel form of apparatus which I have successfully used in practising the process.

Referring now to the drawings,

Figure 1 is a front elevation of the apparatus above mentioned showing two condensers mounted therein; and

Fig. 2 is a side elevation of the apparatus shown in Fig. 1.

'The apparatus shown in the drawings comprises a clamp consisting of a frame 2 having a base 3 adapted to rest on a suitable support, and also having two bolts 4-4 threaded through the upper part thereof.

The clamp is intended to accommodate twocondensers at a time, as shown in Fig. 1, the particular condense-rs shown being .of the wax (preferably par'afiin) type, in which the insulating filler used between the sheets of mica and tin foil consists preferably of parafiin or wax. The invention may be applied,

temperature of the m1ca,'thereby lowering the presence or voids, bubbles, or an unnechowever, to condensers employing other forms of insulating filler, such as adhesive its dielectric strength to such a point as to varnish. cause it to break down and thus short cir- At this point in the process of manufac-, cuit the condenser. ture of the condenser, the condenser stack With a view to avoiding, so far as possible, has been assembled and the condenser units connected together in the desired'manner. The condenser stack 5 next may be mounted in the casing 6 in which it is to be permaheretofore to apply pressure by means of a .nently secured, and in the usual form of clamp to the condenser stack in such a dicondenser in which one terminal is grounded rection as to force the she s f ca. and to the casing, this terminal is then secured sufficient intensity to substantially raise the' essary thickness of insulating filler between, the condenser elements, it has been proposed i cense? at this point in the process to the casing. plished far more efie ct-ually when the pres- For the purpose of. filling the casing with sure onthe stack-is resiliently applied and wax a false head 7 is fitted on the upper end maintained during the heating and subseof 'the casing. This false head is provided quent cooling of the stack, that is, when a with a bridge piece s wliibh is drilledto respring or its equivalent is interposed between ceive a plunger 9 carrying a pressure plate the pressure transmitting parts. The ex- ,10 at its lower end, the pressure. plate restplanation appears'to be that the height of the i ing on the upper-end of the condenser stack stack varies during the heating-and subse- ,5 and, as illustrated, covering substantially quent cooling operations, due largely to the the entire active area of the stack. Pressure squeezing out of the gas, vapor, or excess is applied to this stack by means of the wax from between' the elements of the stack.

' screw 4 and a double leaf spring 12 is inter- "posed between' the lower end of this screw spring 12 islocated in a counter bore in and the upper end of the plunger. 9 so that the pressure isresiliently applied to the condenser stack. A coiled spring 14 encircling, the plunger S-immediately below the legf t e bridge piece 8 and acts on the lower end of this'counter bore to press the false head? firmly against the upper surface of the easthus maintain a tight joint be:

After the parts '1 have been assembled in the manner illustrated, the casing 6 and false head? are substantially filledwith wax silffficiently-heate'd to'be. molten; The'bolt or screw 4 is turned down until the'leaf spring 1 2 is'compressed to such a point that thedesired degree of pressure is applied to the condenser stack, this pressure tending to force the-sheets of micaand foil firmly into'oontact with each other. Any desired degree of pressure can be applied in this manner,that usuallyemployed being about 2,000 pounds. While this pressure is maintained on the stack, heat is supplied 'to-the casing until the fluid wax therein has been'heated to a temperature of approximately 135". 4 wax is heated up slowly so that the tempera- C. The

- ture' of the stack will rise substantially in unison with that of the wax. The heat supplied as above is specially, desirable when the insulating materialused is parafiinsas preferred and when the molten parafhn in the casing has been cooled byits' contact with.

" the previously unheated stack, all in order that-the Waxbetween the sheets may be made suficiently fluid to permit its being squeezed form of apparatus, it is obvious that the 115 high temperature'to which the stack is sublratus and jected will greatly expand any gas or vapor 5 pocketed between the'sheets of mica and an.

that make up the stack and will also melt the waxbeween th'ese'sheets, while-the heavy pressure applied .to the stack willsqueeze the gas or vapon'andany surplus" wax out from between'the sheets. Invother words,

the efi'ect will be to practically eliminate the presence ofany gas or vapor-from between the elements'ot the stack and w reduce to a minimumv the film of wax still remaining between these elements.

I have discovered that this'result is accom- If the pressure is rigidly applied when the apparatus is assembled a reduction in the height of the stack effects a corresponding reduction in the pressure maintained on the stack. The resilient application of this pressureensuresthemaintenance of a substantially constant pressure on the stack during the entire heating and subsequent cooling operation notwithstanding any variation in the height of the stack that may occur during said operations.- The result is a more thorough elimination of the gas, vapor, or excess insulating filler from between the tale ments of the stack.

After the stack has been heated up to the desired temperature, preferably approximately 135 to 145 C.- the wax may be poured'outof the casing. 'Usually it takes about twenty minutes .to-heat the wax to the desired temperature. The resilient pressure is maintained on the stack during the subse-- quentcooling operation, this embeddingof the stack in its casing, which consists in fi-ll ing the casing and head with molten wax and allowing it tocool and solidify, the head and surplus Wax 'then being removed. The .maintenance of the resilient pressure 'on' the stack while it is-cooling ofi, ensures that the alternate layers of mica and foil'will be kept in intimate contact with each other while the wa is solidifying where it will serve to hold the condenserv elements in this intimate relationship, if, during any subsequent step in the process of manufacture, it becomes necessary to remove the pressure from the stack. While l have herein described the process of this invention in connection with a certain process is. independent of any specificappaaid of a great variety of forms of apparatus,- and a great variety of accompanying process steps; .Also, while mica and metal foils constitute the best form of condenser within the invention (the mica and foils both being substantially incompressible), the invention includes the substitution of sheets of equivalent material.. Whatis claimed as new is:

non-porous and substantially;

that it may be practised with the 1. In thev art of making electrical condenser stacks of sheets of substantially nonporous and incompressible dielectrics and conductors, the improvement in cleansing the surfaces of the sheets in the stack by squeezing out a fluid insulating material from the th1n spaces between the sheets lying face to face, which' consists in initially applying a squeezing-out pressure to, the

stack in a 'resilient manner; and then for a substantial period of timeyand during the presence of the fluid insulating material between the sheets, permitting the initial pressure to followup with substantial constancy the gradual contraction of the stack'consequent upon the gradual squeezing out of the fluid insulating material from between the st antly maintained pressure.

sheets and the gradual forcing of the sheets I toward one another by means of such con- 2. In, electrical condensers comprising stacks of sheets of mica and metal foil. the

improvement in excluding foreign matter [from between the sheetslying face to face :in the stack upon reduction of temperature and contraction of the length of the stack, which consists in .initially and resiliently applying pressure across the ends of such a stack prior to such reduction of temper-- ature and contraction of length; and thereafter, and during such cooling, permitting such pressure to. follow with" substantial constancy the variation of the length of the stack consequent upon such cooling.

3. In electrical condenser stacks of sheet-s of mica and metal foil, the improvement which consists in permitting the action on such stack of a resiliently applied pressure" of the order of thousands of pounds while the stack is submerged in insulating material-which is solid at ordinary temperatures but then is fluid' at a temperature'of the order of about one hundred and forty degrees Centigrade. v

4. In electrical condensers comprising stacks of sheets of'mica and metal foil, the

' improvement in effecting and maintaining cleanliness of the surfaces of the sheets of the stack, by. squeezing out from the thin spaces between the sheets lying face to face,

an insulating material which is 'solidatordinary temperatures but fluid atmoderately high temperatures. and'thereafter excluding such material from between the sheets,

which consists in heating such a stack for 'a substantial period of time while such insulating material is present between the sheets; simultaneously with suchheating permiting a resiliently applied sque'ezing out pressure to follow up with substantial constancy the gradual contraction of the stack consequent upon the gradual squeezing out of the fluid material from between the sheets and the gradual forcing of the sheets toward one another by means of such constantly applied pressure; and thereafter permitting the continuing action" of said resiliently applied pressure during the cooling of the stack,

material and the submerged stack for a sub- 5. In the art ofmaking electrical condenser stacks of sheets of mica and metal foil,

the improvement in effecting and maintaining cleanliness of the surfaces of the sheets in the stack by squeezing out from the thin spaces between the sheets lying face to face, an insulating material which is solid at ordinary temperatures but fluid at moderate-- ,ly high temperatures, and thereafter eX eluding such material from entering between the sheets, such improvement consist-t I 111g in submerging such a stack in such 111- I sulating material in hot fluid condition,

supplying additional heat to the insulating stantial period of time; and in the presence of such'insulating material in hotfluid condition between the sheets, permitting a resiliently applied pressure to follow up with substantial constancy the gradual contraction of the stack consequent upon the gradual squeezing out of the fluid insulating material from between the sheets and the gradual forcing of the sheets toward oneanoth er by such constantly applied pressure; and

which process consists in heating the stack' suiliciently'to reduce said adhesive material to a more. or less-fluid condition, exerting a pressure-resilientlyon said stack in the di'-' rection-of its height while the stack is hot, and maintaining said conditions of pressure and temperature on the stack for a sufficient length of time to squeeze out the insulatingwmaterial and any other deleterious things from between the sheets of the' stack and bring said sheets into intimate contact with each other. j

7. That improvement in the process of,

making electrical condensers of the type in which alternate sheets of metal foils and -1nica'are assembled to form a stack with insulating material between the sheets which is solid at ordinarytemperatures and fluid at moderately high temperatures, w ieh consists in heating the stack sufficient y to l'iquefy said insulating material, subjecting said stack to aheavy spring pressure while .it'is so heated, maintaining said conditions of temperature and pressure on thestack for a suflieient lengthof time to squeeze out the insulating material and any other deleterious things from between the elements of the stack and maintaining said resiliently applied pressure to acton the stack while'it. cools.

' 8. In theia t of making electrical conjtionof the stack consequent upon the grad-i ual squeezing out of the fluid lnsulatlng ma denser stacks of'sheets of. mica and metalfoil, the improvement in cleansing the surfaces of the sheets in the stack by squeezing out from the thin spaces between the sheets lying face to face, an' insulating material I which is solid atordinary temperatures-butfluid at moderately high temperatures, such improvement consisting in heating such a stack for a substantial period of time while the sheets and simultaneously with such heating permitting a resiliently applied,

squeezing out pressure .to follow up I with substantial. constancy the gradual contrac- I terialfrom between the sheets and the grad:

.u'al forcing ofthe sheets toward one another. I p I .rialin a fluid condition at a moderately high temperature but which is solid at" ordinaryy' ean sjof such constantly ap li d Pres- 'Sure.' .-1=" 4 I 9. Theiherein described method cwhicli consists in.-.initially and resiliently applying a pressure across the ends of aj condenser stack of. sheets 3 of mica and metal" foil, at. a

- time fwhenthe stack'is at an ordinary tern I peraturefia'nd thereafter permitting such pressure gradually'and with substantial con! from between them. r

stancyto "follow. up variations in length of the stack consequent upon changes in its; I

sulatmgmaterlal aro temperature and thereby J maintaining the i .sheets' in such intimatei relation to one another I as I to exclude everything deleterious 10. The combination of a with-sheets of metal foil-and mica,:of a pressure p'l'ate arranged to-actover theactive I ,are'a'ofthe sheets insaid stack;and a sprin clamp acting-against said pressure plate an arranged to be free to exert substantially constant pressure on said stack via said pressu re plate forall variations of lengthof the.-

stackdue to changes its temperature. 5

'- 11. The combination of a condenser stack surrounded -with an, insulating material" said pressure means andsaid h comprising sheets of metal foil and mica.

which isfsoli'd, at ordinary temperatures and fluid at moderately, high temperatures, and a springclamp therefor constructed and I ranged to exert resiliently a distributed press pressure, and while under said pressure surroundin-g said staekwith hot molten insusure over the active areaof said sheets in the stack to follow. upga'nd yield to variations in length of the stack and maintain the pressure thereonlsubstantiallyconstant; A '12. An apparatus .ad'aptedafor use in. the

for permittingresilientlpressure to act on the stack and aspring.' nterposed between sad for hold-.

I ing said head on the casing."

. 13. The 1m ro'vement: in the:"pro'cess of gnaking electrical condenser stacks ofsheets Y 5 of mica and metal .foil,--which"consists in] varied without I applied pressure. such insulating material is present between condenser stack let. Inthe'art of making electrical. con- ;d'enser stacks of sheets of mica and metal foil, the improvement in'excluding injurious things. from between the ,sheets lying face to face in the stack, which consists in permittinga resiliently applied squeezing out pressure to. force thesheets toward one another. in the presence, betw en the-sheets and around the stack, of an in lating mate- -temperaturesi; an Permitting the continusqueeziug out-of the fluid insulating mate- 'Iliiil from between the sheets and the gradual .forcing of the sheets toward one another, and

ing action of-such resiliently.- applied. pres .sure atteriithas resulted 'in the'gradual during the'cooling of the insulating materialsurrounding thestack, the cooling of] the stack itself, andfthesolidifibation of the inbedment therefor.

'95 d theistack as anein- I 15. That improvement in the process oi makingelect'rical. condenser stacks of sheets of mica and metal foiltreated with insulating materialwhich consists in resiliently applying squeezingout pressure and heat to and surrounding said stack with fluid. insutinued action of said spring pressure, thereby permitting contraction of the stackwithout substantial I altera'tionf in pressure thereon. I Y

16. Thatimprovement in the process'of making electrical condensers which consists in subjecting a stack of sheets of. mica and metal foil to a bath ofhot molten insulating material. while compressed under spring denser stacks of sheets of .mica and metal I foil, the improvement in cleansing the sur- 'saidstack to drive out the insulating matenrial progressively from" between the sheets,

lating .material j'while permitting the con-f faces of the sheets in the stack by'squeezing' out from the thin-spaces between the-sheets lying face to face; -a ffluid, insulating. mate rial at moderately high temperature which is solid at ordinary:- temperatures, such. im-

neeaew condition. between; v the sheets; permitting a resiliently applied squeezi em pressure to follow up with suhsntifi upon the gradual squeezing out of the fluid insulating material from between the sheets and the adual forcing of the sheets toward one anot er by such constantly applied pres sure. v18. In the art of making electrical condenser stacks of sheets of mica and metal foil, the improvement in cleansing the sur eonstancy the gradual contraction of the stack. consequent faces of the sheets, which consists in forming a stack of such sheets with" insulating to material betweenthem which is solid at ordinary temperatures but fluid at moderatel high temperatures; applying heat to sue stack for a substantial perie substantial constancy the gradual contractioin of the stack consequent u. on the grade ua another b such ccnstantl 'appliedpressure. In testimony whereof have signed my name to this specification.;. FRANCIS W. DANE.

of time; and,

while the insulating material between the 25 sheets is "in fluid condition, permitting a resiliently applied pressure to fellow up with ueezing out of the fluid insulating 30 material .frem between the sheets and the -dual forcing of the sheets toward one 

